The present invention relates to a transportation container for electronic components. It particularly relates to such a container suitable for sending through the mail. In greatest particularity it relates to a container for components requiring electrostatic shielding during transportation.
Electronic components nowadays comprise a large number of metal oxide silicon (MOS) devices which are sensitive to electrostatic discharge. A few hundred volts discharging to a portion of an integrated circuit or a board bearing such an integrated circuit can cause instantaneous failure of an electronic device. Such discharges are invisible and frequent in most environments which would, for all other purposes, be considered normal. Accordingly, it is necessary to apply stringent electrostatic precautions when handling integrated circuits or electronic component boards of this type.
It is necessary for repair and maintenance of equipment to send replacement boards to service personnel to replace damaged boards in equipment. No matter how careful the packers may be to avoid electrostatic damage to the board, there is no guarantee that circumstances during transit or precautions taken when the transportation container is opened will not place the board at risk of destruction by electrostatic discharge. Accordingly, the present invention seeks a low-cost transportation container generally suitable for use with all types and sizes of electronic components or circuit boards wherein the risk of electrostatic discharge during transit or unpacking is minimized.
The present invention consists in a transport container for electronic components comprising: an inner box having, as elements, a base, first and second sides, first and second ends, and a lid; said box being formed from a single, planar sheet by folding; said planar sheet having an electrically conductive, continuous, elastic layer on a face thereof; said container further having a conforming outer sleeve for holding closed said box when said sheet is folded to form said box; where, when said sheet is folded to form said box, said face of said sheet forms the inside surface of said box; and where said layer deforms along abutting edges of said elements to seal open seams between said elements to cause the interior of said box to be completely surrounded by electrically conductive material.
The different shipping requirements for electronic components mean that sometimes a very small item must be shipped and at other times a bulky item must be shipped. In order readily to accommodate any size of item the preferred embodiment of the present invention provides that, when the box is closed with no enclosure therein, the surface of the layer on the lid is in uncompressed tangency with the surface of the layer on the base. This means that, should a very tiny item be placed within the box, it will still be gripped and held in place by the electrically conductive layer on the lid pushing against the electrically conductive layer on the base. On the other hand, when a larger item is placed within the box, the layer elastically deforms to accommodate the item.
Use of foam and foam blocks within boxes requires careful sculpting of the foam and adds to the cost of construction of the transportation container. In order to overcome the problems associated with foam, the present invention provide a transportation container wherein the electrically conductive layer is a bubble sheet with a flat side on the face of the folded sheet and a plurality of gas filled bubbles protruding from the face of the sheet. The present invention further provides in its preferred embodiment that the bubbles can burst to accommodate any prominences in any enclosure. The bursting of bubbles creates a cavity wherein the prominence is accommodated and held in place by adjacent unburst bubbles. The item having such prominences is thus immobilized and held in place in the box and the bubble layer automatically comes into conformity with the surface of the enclosure either by deformation of the gas filled bubbles or by actual bursting of bubbles.
When a transportation container is unpacked, the interior of the box has, up until that time, formed a Faraday cage (i.e. a space completely surrounded by electrically conductive material) wherein no electrostatic field can form. As soon as the enclosure is removed from its Faraday cage, it rapidly assumes the voltage of the surface of the cage. Should the voltage on the surface of the cage be markedly different from the voltage or electrical potential of the surroundings where the transportation container is open, as soon as the enclosure is brought into proximity with the surroundings a spark can pass and destroy the electronic item, now unpacked. Accordingly it is important that the conductive layer be brought to the same electrical potential as its surroundings when the transportation container is opened. Accordingly the preferred embodiment provides that the electrically conductive layer, at any sealed open seam in the box, protrudes from the open seam to allow electrical contact therewith. This electrical contact can either be deliberate (in the case of a careful operative opening the box) or can be accidental. The present invention provides the maximum opportunity for accidental contact between the electrically conductive layer and the operator so that, should the operator (who is generally grounded) forget to discharge the electrically conductive layer to ground, there is still ample opportunity for accidental discharge of the electrically conductive layer to have taken place.
Further to facilitate discharge of the electrically conductive layer, the present invention provides that the box has an aperture in the folded sheet which allows access to the electrically conductive layer. In the preferred embodiment the sleeve has an opening and the opening comes into registration with the aperture when the box is in the sleeve. Direct access to the electrically conductive layer may thus be made through the sleeve even when the box is closed. This allows touching of the layer with a grounded probe or other instrument before the box is opened. In the preferred embodiment of the present invention the sleeve has a plurality of openings so that the aperture in the box can engage one of the plurality of openings whichever one of the plurality of orientations is used to insert the box into the sleeve.